Electroless deposition of metals

ABSTRACT

This specification discloses a method for electroless deposition of a metal upon a substrate. The substrate is one that has a catalytic surface capable of influencing deposition of the metal. The method involves mixing the substrate with a solution comprising a pi -complex of the metal to be deposited on the substrate dissolved in a nonaqueous solvent. There is also added to the solution a reducing agent such as hydrogen. The reducing agent effects reduction of the complex thereby decomposing the complex to form elemental metal. The elemental metal then deposits on the substrate.

I United States Patent 1151 3,635,761 Haag et a1. Jan. 18, 1972 54] ELECTROLESS DEPOSITION OF 2,719,799 10/1955 Rosenblatt et a1. ..117/54 x METALS 2,853,398 9/1958 Mackin et al. .117 47 2,922,803 1/1960 Kaufman 260/429 [72] Inventors: Werner 0. Hang, Trenton; Darrell Duayne 2,930,807 4/1961 case X whitehurs" Tlmsvlne, 2,980,741 4/1962 Zeiss et al. ..260/429 x 73 Assignee; Mobil on Corporation 3,083,109 3/1963 Rhodes et al. ..1 17/160 X 3,147,154 9/1964 Cole etal ....117/l13 I221 May 5,1970 3,151,140 9/1964 I-lubel et al. ..260/429 21 APPL No 34 3 3,159,658 12/1964 Fischer et al. ..260/429 3,265,520 8/1966 Obenschain ..1 17/160 Related US. Application Data FOREIGN PATENTS OR APPLICATIONS [63] Continuation-impart of Ser. No. 647,222, June 19,

1967, abandon 676,894 12/1963 Canada ..117/54 1,028,408 5/1966 Great Britain ..260/429 52 us. 01. ..117/227, 106 1, 117 47 R, 1,058,679 2/1967 Great Britain 160/429 117/47 A,117/100B,117/l00A,1l7/IO0C, I 117 100 M, 117 100 5, 117/130 E, 117/13s.s R, Primary Examinerwilliam Martin 1 7 13 3 N, 1 7 3 5 1 7 1 R, 2 9 429 R, Assistant ExaminerMathew R. P. Perrone, Jr.

2 0/429 Y AttorneyFrederick E. Dumoulin, William J. Scherback, 51 Int. (:1. ..C23c 17/02 Oswald Hayes and Andrew Gaboriault [58] Field ofSearch ..117/47, 54,100,113,160,

117/130, 227; 260/429 R, 429 CY; 106/1 ABSTRACT This s ecification discloses a method for electroless de osi- [56] References cued tion 0t a metal upon a substrate. The substrate is one that l ias 21 UNITED STATES PATENTS catalytic surface capable of influencing deposition of the metal. The method involves mixing the substrate with a solu- Beer X {ion comprising a ucomplex of the metal to be deposited on 3,295,999 1/1967 Klein at 17/47 X the substrate dissolved in a nonaqueous solvent. There is also 3,402,067 9/1966 Langley 17/160 added to the solution a reducing agent such as hydrogen. The 3,415,666 12/1968 Nagai et -106/l reducing agent effects reduction of the complex thereby 3,418,346 12/1968 Parshall ..106/1 decomposing the Complex to form elemental memL The 1 3,457,089 7/1969 Shipley et a1. ..106/1 mama] meta] then deposits on the substrate 3,387,009 6/1968 Bublitz et al..... ..260/429 2,702,253 2/1955 Bergstrom ..1 17/54 20 Claims, No Drawings ELECTROLESS DEPOSITION OF METALS CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of our copending application, Ser. No. 647,222, filed June 19, 1967, now abandoned.

Chemical reactions catalyzed by materials prepared in accordance with this invention are disclosed and claimed in copending application, Ser. No. 672,008, filed Oct. 2, 1967, now abandoned in favor of application, Ser. No. 57,796, filed July 23, 1970. Certain products prepared inaccordance with application, Ser. No. 647,221, filed June 19, 1967, copending with said application, Ser. No. 647,222 of which the present application is a continuation-in-part as indicated above, and now abandoned in favor of a continuation-in-part application, Ser. No. 22,362 filed Mar. 24, 1970, are useful as substrates or supports in the present invention.

BACKGROUND OF THE INVENTION 1. The field of the invention comprises electroless deposition.

2. There is an increasing search for ways of coating objects which cannot be electroplated, either because they are nonconductors, like plastics, or because they are too small to attach electrodes economically, like printed circuits. For coating metals on specialized surfaces like the foregoing, electroless deposition has come to be of value, and while it is a known operation, the published literature does not show it to have been used to deposit platinum, or to deposit platinum and other metals on very finely divided substrates for the purpose of preparing catalysts and other products.

SUMMARY OF THE INVENTION DESCRIPTION OF THE SPECIFIC EMBODIMENTS The useful metal pi-complexes are broadly characterized by the presence ofa central or nuclear metal atom having bonded thereto at least one ligand in the form of an organic group containing at least one carbon-to-carbon multiple bond. By virtue of the multiple bond, which is either a double or a triple bond, the group is bonded to the metal through the pi electrons of the bond, the resulting attachment being described as a coordinate covalent bond. The sigma electrons of the multiple bond provide a carbon'to-carbon attachment described as a covalent bond. The unsaturated organic group is preferably an unsaturated hydrocarbon group, or one derived therefrom, i.e., a substituted unsaturated hydrocarbon group, and it preferably has two or more of said multiple bonds. The central metal atom is preferably platinum or palladium or other transition metal.

Usually, and as is preferred, the complex also contains one or more other ligands different from said organic group and which may be either anionic or neutral, and preferably singly charged, such as a halide ion. A specific illustrative complex is l,5-cyclooctadieneplatinurn (ll) dichloride, the structure of which may be represented as follows:

where the arrows represent coordinate covalent bonds linking the double bonds of the hydrocarbon moiety to the Pt, and the Cl atoms are connected to the Pt by covalent bonds. A convenient and illustrative way of defining the useful complexes is by means of the expression where R is the unsaturated organic group or ligand, M is the central metal atom, X is the anionic or neutral ligand described above as the other ligand, and m and n are integers.

As indicated, R is preferably an unsaturated hydrocarbon group, which may or may not be substituted by one or more substituents. Preferred unsaturated hydrocarbon groups are olefinic ligands derived from open chain diolefins having three to 24 carbon atoms, particularly unconjugated diolefins like 1,5-dienes, and including allene, butadiene, isoprene, pen tadiene, hexadiene, heptadiene, diisobutenyl, decadiene, and the like. Other preferred unsaturated hydrocarbon groups are derived from open chain olefins having more than two double bonds, some times designated oligo-olefins, such as hexatriene, 2,6-dimethyl2,4,6-octatriene, etc. Also preferred are cyclic diolefrns and cyclic oligo-olefms, particularly unconjugated compounds like l,5-cyclodienes, and including cyclobutadiene, cyclopentadiene, fulvene, norbornadiene, cyclooctadiene, dicyclopentadiene, 4-vinylcyclohexene, limonene, dipentene, cycloheptatriene, cyclooctatriene, bicyclo(2.2.2)octa-2,5,7-triene, cyclononal ,4,7-triene, cyclooctatetraene, and the like. Also useful are groups derived from heterocyclic diand oligo-olefins like heterocyclopentadiene," which is intended to refer to all five-membered ring systems in which a hetero atom like phosphorus, oxygen, iron, nickel, cobalt, etc., replaces a methylene group of cyclopentadiene. Other suitable unsaturated hydrocarbon groups are derived from the acetylenes such as the hexadiynes, heptadiynes, octadiynes, l,8-nonadiyne, 4,6-decadiyne, dodecatriyne, and the like. Unsaturated hydrocarbon groups having both double and triple bonds are of value, such as butenyne, 1,6-heptadien-3-yne, 3,6-dimethyl-2,6-octadien-4- yne, l,7-octaenyne, etc. Or a mixture of an olefinic ligand and an acetylenic ligand of the foregoing types may be suitable.

It may be seen that R, the unsaturated hydrocarbon group, may have two or more double and/or triple bonds, and may have an open chain or a cyclic structure. In some case, R may be an unsaturated cyclic or heterocyclic having one double bond, or it may be a monoolefin having two or more carbon atoms such as that derived from ethylene, styrene, and the like; or it may be a monoacetylenic acetylene group; or an aromatic ligand like benzene or phenyl. It was also indicated that R may have various substituents, and these may include alkyl, aryl, alkoxy, halogen, carboxyl, ester, keto, and the like, it being understood that, as so substituted, the resulting substituted R group is capable of pi-electron bonding to the metal atom M.

In formula (II), the atom M is a metal. Metals which can be employed are the metals of Groups VIII, lB, IVB, VB, VlB, and VIIB. The metals of Group IIIA except boron may also be employed. The metals of Group VIII are iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum. The metals of Group 18 are copper, silver, and gold, of Group IVB are titanium, zirconium, and hafnium, of VB are vanadium, niobium, and tantalum, and of WE are chromium, molybdenum, and tungsten. The metals of Group VllB are manganese and rhenium. The metals of Group IIIA, except boron, are aluminum, gallium, indium, and thallium. Particularly preferred metals are palladium, platinum, and aluminum.

Group X of formula (ll) is preferably a halidelike Cl, Br, F, and I. Other suitable groups are alkyl, acyl, amine, ammonia, acyloxy, alkyl sulfide, aryl sulfide, carbonyl, cyanide, isocyanide, hydrogen sulfide, nitrosyl, hydroxy, phosphine, thiocarbonyl, thionitrosyl, and water. Also amide, aryloxy, aroyl, aroyloxy, alkoxy, hydride, hydrogen sulfite, thiocyanate, etc.

The group R in formula (ll) is an anionic group if it loses a proton; and if no proton is lost, it is treated as a neutral group. In computing the oxidation number of the central metal atom, the group R if anionic, is counted as negative; if neutral, it is counted as having zero charge.

In general, it may be noted that the preferred ligands R and X are those that do not contaminate the metal surface, either because of their nature, such as alkoxy and acyloxy ligands, or because they pass off as gases, such as Cl and Br which pass off as l-lCl and HBr, or because they are converted under reaction conditions to compounds that do not contaminate, such as olefms and dienes which form saturated hydrocarbons.

The number of R and X ligands are denoted by the subscripts m and n; thus m may vary from I to 8, and n from 7 to 0, while their sum varies from 2 to 8. These variations, of course, are determined by the nature of the metal M and by its state of oxidation. The oxidation state of the metals as a group may range from to 8, it being understood, as a glance at the periodic table will show, that some metals exhibit more oxidation states than others. It should be remembered thatsome v ligands may have two bonds attached thereto. It will be seen that at least one R group is always present in formula (II).

When n is 0, the formula becomes R,,,M, where m may vary from 2 to 8; in complexes of this type, M is usually a metal of Group VIII or is chosen from chromium, titanium, rhenium, or vanadium. Preferred complexes are denoted by such formulas as RMX RMX RMX R MX R MX and R MX Generally, and as is preferred, the useful complexes have one central or nuclear metal atom; however, the invention also contemplates complexes having two such atoms, either the same or different, as in azulenehexacarbonyldimolybdenum, C, l-l,,Mo (CO) or in l,3-bis-(styrene)-2,4-dichloro- ,u-dichloro-diplatinum (ll), C, H, Pt- C,.,, and the complex is designated a dinuclear complex.

Some illustrative complexes may be listed as follows, and an additional list appears in example 5:

. dicyclopentadieneplatinum(ll) dichloride l,3-butadienepalladium( ll) dichloride 1,3,5-cycloheptatrieneplatinum(II) dichloride norbornadienepalladium(ll) dibromide 1,3,5 ,7-cyclooctatetraeneplatinum(ll) dichloride 2,5-dimethyl-l,5-hexadieneplatinum(ll) dichloride bis(1r-allylnickel iodide) l,5-cyclooctadienegold(lll) trichloride 9. (l,7-octadiyne)platinum(ll) dichloride A complex like No. l in the foregoing list may be prepared by adding dicyclopentadiene to Zeises acid, H(C H PtCl and refluxing for several hours, thereby to precipitate the complex. A complex like No. 2 may be prepared by using the method of Kharasch et al. JACS 60 882-4 (1938), as extended in Inorganic Synthesis Vl 218-9, which involves using palladium(ll) chloride as a starting material, reacting this with benzonitrile, and then reacting'the resulting product with 1,3- butadiene. When carbonyl groups are present, as ligands, the corresponding metal carbonyl may be used as a starting compound and reacted with a suitable olefinic material. Other methods for preparing the complexes are available.

Turning to the electroless method of depositing metal on a substrate, the desired complex is suitably dissolved in a nonaqueous solvent, the substrate is mixed with the solution and is, of course, insoluble therein, and then a reducing agent like hydrogen gas is bubbled through the mixture for a suitable period of time sufficient to reduce at least a portion of the complex to form elemental metal. Substantially all of this metal deposits on the substrate, and the resulting coated substrate comprises the product. Good stirring of the solution should be used. The following factors are considered noteworthy: the surfaces of the substrate are believed to catalyze the deposition of metal thereon; a reducing agent for the complex is present; more than a monolayer of metal is deposited on the substrate, i.e., the metal continues to deposit as long as any complex is present to be reduced; and the metal deposits only on the substrate, substantially none being deposited in the solution external to the substrate, or on the walls of the vessel, or on noncatalytic surfaces of other solids that may be present. The last factor, in particular, enhances the economics of the method as it eliminates waste of metal.

Suitable nonaqueous solvents include alkanes like hexane; aromatics like benzene (preferably thiophene-free) and toluene; halogenated alkanes and aromatics like trichloroethane, chlorobenzene, chloroform, and carbon tetrachloride; esters like methyl and ethyl acetates; ethers like dioxane and diethyl ether, ketones like acetone and methyl ethyl ketone. Of the foregoing, the chlorinated alkanes; aromatics, ketones, and ethers are preferred. Also contemplated are nitroalkanes. Other things being the same, a more volatile solvent is to be chosen as against a less volatile one in order to facilitate its removal at the end of the deposition step.

Hydrogen is the preferred reducing agent as it is not only effective but, being gaseous, does not remain in the reaction mixture. Other agents that may be used include formic acid, and alkali metal hydrides and borohydrides. Also dibenzyl, hydrazobenzene, hydroquinone, and various hydroaromatics, like cyclohexene, tetralin, 2-cyclohexene-l-one, 4-vinylcyclohexene, cyclohexadiene, and other partially saturated cycloalkenes; also p-menthadienes such as limonene, the terpenes, etc., also l,4dihydro-N-benzylnicotinamide.

In other cases, the unsaturated hydrocarbon group, R in formula (ll), may act as the reducing agent for decomposing the complex, as frequently R is a hydroaromatic moiety. Thus, in order to decompose the complex, it is heated in the presence of the solvent, and the substrate, thus depositing free metal on the substrate. The ligand X, if it is group like Cl, may react to form HCl, which under the reaction conditions can leave the reaction mixture as a gaseous product.

The substrate may be any suitable solid porous or nonporous material which provides a catalytic surface capable of influencing deposition of the metal and which, of course, is insoluble in the solution of the complex. It may have any suitable shape, ranging from a powdered or granular material to larger objects, including screens and sheet material. Desirably, the substrate is a material or object or device which, when coated with metal, forms a useful product such as a catalyst, an electronic component, a metallized plastic, etc. Quantitative deposits of metal have been obtained on substrates like platinum foil, particles of alumina having a thin layer of platinum, cation exchange resin particles having a thin palladium or platinum coating, alumina particles coated-with palladium, gold foil. If a substrate does not originally have the desired catalytic surface, such a surface may be formed by placing on it a layer of a catalytic metal like platinum or palladium, etc., as illustrated in example 3. It should be pointed out that a substrate which initially has a catalytic surface does not lose it, after metal deposition begins, as the deposited metal exercises a catalytic influence. By way of illustration, preferred substrates comprise particulate materials having a particle size in the colloid size range, which is considered to extend from 10 to about 10,000 angstrom units. Other preferred illustrative substrates may be larger, ranging from 0.5 micron to 0.25 inch in diameter. The substrates may include materials like the crystalline aluminosilicate molecular sieves; inorganic metal oxides like alumina, silica, silica-alumina, thoria, vanadia, zirconia, titania, zinc oxide, etc.; also boron nitride, pumice, silicon carbide, etc.; also cellulose and glass; and various polymers like the polyolefms, fluorinated hydrocarbon polymers, polyamides, polyesters, etc. Also suitable are ion exchange resins; and conducting materials like graphite, carbon black, powdered metals like copper and silver, fine mesh metal screens, etc.

The temperature of the electroless deposition generally varies from room, or somewhat below, to refluxing tempera tures. With normally liquid reducing agents like formic acid the temperature may range to 100 C. or more; and with some agents the temperature can go up to 200 or 300 C. or more. The temperature should not exceed the thermal decomposition point ofthe complex, which may be above 200 or 300 C. The time required for the deposition is variable and will depend, together with the temperature, on the complex and its amount, among other things; generally the time may extend over a period of several minutes to several hours. In respect of concentration of the complex in the deposition solution, it may be stated that higher concentrations favor higher deposition rates. Both lower and higher concentrations are useful to deposit small amounts of metal, but at lower concentrations less control is involved. Numerically, the concentration may vary over a wide range, going from about 0.01 percent by weight, or less, to saturation. As for the substrate concentration, there are no practical limits. The deposit may vary in thickness from one or a few monolayers, or even from an incomplete monolayer, to any desired thicker deposit. Generally, hard and smooth deposits intimately bonded to the substrate surfaces are obtainable; these may be controlled to have a bright or a rough finish. The deposits may be as complete and continuous as desired, thus providing for good electrical conductivity. In the case of porous substrates, metal is depositable on the surfaces of the internal pores.

As described, it is preferred to deposit all or substantially all of the metal on the substrate, with none being deposited in the external solution. In some cases, i.e., when hydrogen is used as reducing agent and in the presence of certain complexes made from monoolefins, such as l,3-bis-(styrene)-2,4-dichloro-p.-

dichlorodiplatinumfll); or when hydrogen is used as reducing agent and in the presence of hydroxylated solvents like alcohols or carboxylic acids, deposition of metal may take place partly on the substrate and partly in the external solution. This type of deposition may be useful for some purposes, as where it is desired to make a catalyst comprising a mixture of (1) particles comprising a metal-coated substrate, especially where the amount of coating is very low, and (2) particles of the metal per se.

It is to be understood that the metal pi-complexes described include complexes having pi-allylic ligands, as illustrated by 1rallyl-1r-cyclopentadienyl'platinum, or by dibenzene chromium.

It should also be understood that the deposition solution may contain two or more different metal pi-complexes each containing the same or a different metal. Where the deposition solution contains two or more different metal pi-complexes, the metal of each of the pi-complexes being different, the two or more different metals deposit simultaneously on the substrate. Thus, a mixture, for example, an alloy, of two or more different metals may be deposited on the substrate.

The invention may be illustrated by the following examples.

EXAMPLE 1 Zeises acid, H(C H PtCl was made by mixing for 30 minutes a solution of 3.175 g. sodium chloride in 20 ml. distilled water with a solution of 13.996 g. chloroplatinic acid in 20 ml. distilled water. The mixture was evaporated to dryness, 100 ml. absolute ethanol added, evaporated again, another 100 ml. of the alcohol added, the mixture refluxed overnight, filtered, and the filtrate diluted to 100 ml. with ethanol. Solids comprising sodium chloride were filtered off, and the remaining liquid comprised Zeises acid dissolved in alcohol.

EXAMPLE 2 A platinum pi-complex was prepared by adding ml. 1,5- cyclooctadiene to 50 ml. Zeises acid solution, as prepared in example 1, and refluxing overnight. A precipitate was formed which was filtered, washed with ethanol, washed with ether,

and dried in vacuo. A yield of 5.35 g. of 1,5-cyclooctadieneplatinum(ll) dichloride was obtained,,m.p. 293-297 C.

EXAMPLE 3 A platinum-coated alumina substrate was prepared by adding 400 g. alumina powder to a solution of 2.0 g. of the complex of example 2 in 1,500 ml. of 2-methoxyethanol; this mixture was stirred, refluxed a few minutes, then cooled, filtered, washed with chloroform and methanol, and dried in vacuo. The resulting substrate comprised particles of alumina having a thin coating of platinum in an amount of about 0.1 percent by weight.

EXAMPLE 4 The complex of example 2 was subjected to electroless deposition in the presence of the substrate of example 3 by first suspending 1.01 g. of substrate in 10 ml. benzene, adding 70 mg. complex thereto, and then bubbling hydrogen gas through the solution over a period of 1 hour. The substrate particles were then filtered, washed, and dried. About 30 mg. of platinum deposited on the substrate. The resulting mate rial, comprising platinum on alumina, was used as catalyst for the hydrogenation of l-hexyne. About 1 ml. of the latter was mixed with mg. of the catalyst and 25 ml. of dioxane, as solvent, and the mixture kept at room temperature for a period of 40 minutes under anatmosphere of hydrogen, with stirring. Thereafter, an aliquot of the mixture was analyzed by vapor phase chromatography, with the result that 92 percent conversion was observed to a mixture of 22 percent n-hexane and 70 percent l-hexene. The reaction was continued for 40 more minutes, then analyzed, and it was found that a 100 per cent conversion to nhexane was obtained.

EXAMPLE 5 Using the procedure of example 2, the following complexes were prepared (see Nos. 1 through 5 in the table below) and tested. Weighed amounts of the complexes were subjected to electroless deposition, using the substrate set forth in example 3 and trichloroethane as solvent. Hydrogen was bubbled through each solution at the same rate over a period of 60 minutes. In each case the amount of substrate was 1 g. and 10 ml. of solvent was used. At the conclusion of the tests, the amount of metal deposited on the substrate was accurately determined. The following data were obtained, including a control in which the substrate was omitted.

tion

In each starting solution, the maximum amount of platinum that could be deposited was 3.65 percent by weight; by comparison with this figure, 17.5 to 56.4 percent of the platinum was deposited. ln run Nos. 1-5, no platinum was deposited in the external solution, as demonstrated by the fact that the complex recovered from each solution contained the nondeposited platinum. In another run, uncoated alumina powder was used as substrate with the result that no platinum was deposited on it, and the complex was recovered unchanged.

EXAMPLE 6 The complex of example 2 was reduced in the presence of the coated substrate of example 3, using various reducing agents, amounts thereof, solvents, reducing times, and temperatures. The results are tabulated below as run Nos. 4 1 through 12. In each case: the amount of solvent was ml., except for Nos. 1 l and 12 where 10 and ml., respectively, were used; the weight of complex was 0.14 g., except for No. 12 where 0.05 g. was used; and the weight of alumina was 2.0 g., except that in No. 12 0.5 g. was present. Also, in each case the reducing agent was dissolved in the solvent; and the temperature was the refluxing temperature of the solution.

The metal depositions in all of these experiments were observed to occur exclusively on the substrate particles.

The resultant materials were then filtered, washed with chloroform, and dried at 1 10 C.

The products of the depositions were analyzed by electron microprobe, X-ray diffraction, and light microscopy with the following results:

The product of deposition A was found to contain a goldpalladium alloy that was about 80 percent palladium.

The product of deposition B was found to contain a goldpalladium alloy that was about 65 percent palladium.

It will be understood that in forming the deposition solution, the sequence of addition of the complex, solvent, or reducing agent, or of the substrate, is not material.

The periodic table classifications used herein are based on the arrangement distributed by E. H. Sargent & Co. and

Weight of Weight reducing Time, Temp, percent No. Reducing agent agent, gms. Solvent hrs C. platinum 1. 2-cyclohexene-1-one 6 132 0. 3

. 181 Chlorobenzene 4 132 084 Ethanol 6 78 73 12. 1,3-cyelohexadiene 16 100 1. 5

0.4 b loxanm The amount of platinum that deposited on the substrate ranged from about 8 to about 88 percent ofthe theoretical.

EXAMPLE 7 reducing agent was employed. About 0.10 g. of 4-vinyl-' cyclohexenedichloroplatinum (ll) was dissolved in 10 ml. of dioxane in the presence of 0.60 g. of the coated substrate produced in example 3. The mixture was stirred for 2 hours at refluxing temperature (100 C.), and a definite observable deposition of platinum on the substrate took place, the metal appearing black. Visual inspection of the particles at the end of the run showed a heavy coating of metal. Thus, the 4-vinylcyclohexene moiety of the complex, under the conditions of the experiment, functioned as reducing agent. When silica gel and uncoated alumina were used as substrates, no deposition occurred, indicating that their surfaces were not per se catalytic.

EXAMPLE 8 This example illustrates the electroless deposition of a goldpalladium alloy. A gold reagent solution (0) was prepared by dissolving 1.77 g. of chloroauric acid in 200 ml. chloroform at the reflux temperature. This solution was then dried by the addition of anhydrous calcium chloride. A palladium reagent solution (P) was prepared by dissolving 2.22 g. of l,5-cyclooc' tadienepalladiumfll) dichloride in 200 ml. chloroform. The substrate for deposition consisted of solid particles of a porous copolymer of styrene and divinylbenzene, which had been sulfonated and the sulfonate groups exchanged to the sodium form. Within the porous matrix of this polymer, zerovalent palladium had been incorporated in catalytic amounts (0.4 percent on a weight basis). The two reagent solutions were mixed in equal proportions, 0.5 g. of the substrate was added, and hydrogen was bubbled through the solutions at room temperature for various lengths of time. The exact proportions of solutions and reaction times are presented in the following table.

Reaction time (min) I0 further identified by the legend Copyright 1962 DynaSlide Co. 1

In the light of the foregoing description, the following is claimed.

What is claimed is:

1. Method for electrolessly depositing a metal selected from the group'consisting ofiron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, titanium; zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rh'enium, aluminum, gallium, indium, and thalliuin on a substrate having a catalytic surface capable of influencing deposition of said metal which comprises mixing said substrate with (I a solution comprising a pi-complex of said metal dissolved in a nonaqueous solvent therefor, said mixing being at a tempera- 5 ture which does not exceed the thermal decomposition point of said complex, and with (2) a reducing agent selected from the group consisting of hydrogen, formic acid, alkali metal hydrides, alkali metal borohydrides, dibenzyl, hydrazobenzene, hydroquinone, cyclohexene, tetralin, 2- cyclohexene-l-one, 4-vinylcyclohexene, cyclohexadiene, limonene, terpenes, and l,4-dihydro-N-benzylnicotinamide, said complex having at least one ligand in the form of an organic group containing at least one carbon-to-carbon multiple bond, said group by virtue of said multiple bond being capable of pi-electron bonding to the metal of said complex, thereby decomposing said complex to form elemental metal, and depositing said elemental metal on said substrate.

2. Method of claim 1 wherein the substrate is a nonconductor of electricity.

3. Method of claim 1 wherein the substrate comprises conducting particles too small to attach electrodes.

4. Method of claim 1 wherein the complex has at least one other ligand different from said organic group.

5. Method of claim 4 wherein said other ligand is selected from halogen, carbonyl, alkyl, acyl, acyloxy, amine, ammonia, phosphine, cyanide, isocyanide, nitrosyl, alkyl sulfide, aryl sulfide, hydroxy, hydrogen sulfide, thionitrosyl, thiocarbonyl, water, hydride, amide, aryloxy, aroyl, aroyloxy, hydrogen sulfite, thiocyanate, and alkoxy.

6. Method of claim 5 wherein the number of said one ligand varies from 1 to 8 and the number of said other ligand varies from 7 to 0, while the sum of the two varies from 2 to 8.

7. Method of claim 6 wherein the number of said one ligand varies from 1 to 2, the number of said other ligand varies from 2 to 6, and the sum of the two varies from 2 to 8.

8. Method of claim 4 wherein said one ligand is derived from an open chain diolefin.

9. Method of claim 4 wherein said one ligand is derived from an open chain oligo-olefin.

10. Method of claim 4 wherein said one ligand is derived from a cyclic diolefin.

11. Method of claim 4 wherein said one ligand is derived from a cyclic oligo-olefin.

12. Method of claim 4 wherein said one ligand is derived from an acetylene.

13. Method of claim 4 wherein said solvent is a nonhydroxylic solvent and wherein substantially all of the deposited metal is deposited on the substrate.

14. Method of claim 4 wherein said reducing agent is hydrogen.

Method of claim 1 wherein said metal is palladium.

16. Method of claim 1 wherein said substrate comprises a particulate material having a particle size in the colloid size range.

17. Method of claim 1 wherein said metal is platinum.

18. Method of claim 1 wherein said metal is aluminum.

19. Method for electrolessly depositing two or more metals selected from the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum,

copper, silver, gold, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, aluminum, gallium, indium, and thallium on a substrate having a catalytic surface capable of influencing deposition of said metal which comprises mixing said substrate with (l) a solution comprising a pi-complex of each of said two or more metals dissolved in a nonaqueous solvent therefor, said mixing being at a temperature which does not exceed the thermal decomposition point of said complexes, and with (2) a reducing agent selected from the group consisting of hydrogen, formic acid, alkali. metal hydrides, alkali metal borohydrides, dibenzyl, hydrazobenzene, hydroquin one, cyclohexene, tetralin, 2-cyclo hexene-l-one, 4-vinyl cyclohexene, cyclohexadiene, limonene, terpenes, and 1,4- dihydro-N-benzylnicotinamide, each of said complexes having at least one ligand in the form of an organic group containing at least one carbon-to-carbon multiple bond, said group by virtue of said multiple bond being capable of pi-electron bonding to the metal of said complex, thereby decomposing said complexes to form elemental metal, and depositing said elemental metals as a mixture on said substrate.

20. Method of claim 19 wherein said metals are gold and palladium.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,635,761 D t d January 18, 1972 Inventor(s) Werner O. Haag and Darrell Duavne Whitehurst It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

References cited:

3,402,067 "9/1966" Langley should be -9/l968--;

"2,719,799" 10/1955 Rosenblatt et al should be --2,7l9,797--; 2,930,807 "4/1961" Case should be --3/l960--;

2,980,741 "4/1962" Zeiss et al should be "4/1961"; 3,265,520 8/1966 "Obenschain" should be --Obenshain-.

Column 2, line 52, "case" should be -cases.

Column 6, line 60, "0. 0738 tom 2.06" should be --0.0738- (under heading reading Complex go) and -2.06-- (under heading reading Pt deposit.

ed Z, by W120 Signed and sealed this 29th day of August 1972.

(SEAL) Attest;

EDWARD MTLETCITER R. ROBERT COTTSCHALK Attesting Officer Commissioner of Patents F ORM PO-IOSO (10-69) USCOMM"DC 60376-P69 U,5. GOVERNMENT PRINTING OFFICE: \969 0-365-334 

2. Method of claim 1 wherein the substrate is a nonconductor of electricity.
 3. Method of claim 1 wherein the substrate comprises conducting particles too small to attach electrodes.
 4. Method of claim 1 wherein the complex has at least one other ligand different from said organic group.
 5. Method of claim 4 wherein said other ligand is selected from halogen, carbonyl, alkyl, acyl, acyloxy, amine, ammonia, phosphine, cyanide, isocyanide, nitrosyl, alkyl sulfide, aryl sulfide, hydroxy, hydrogen sulfide, thionitrosyl, thiocarbonyl, water, hydride, amide, aryloxy, aroyl, aroyloxy, hydrogen sulfite, thiocyanate, and alkoxy.
 6. Method of claim 5 wherein the number of said one ligand varies from 1 to 8 and the number of said other ligand varies from 7 to 0, while the sum of the two varies from 2 to
 8. 7. Method of claim 6 wherein the number of said one ligand varies from 1 to 2, the number of said other ligand varies from 2 to 6, and the sum of the two varies from 2 to
 8. 8. Method of claim 4 wherein said one ligand is derived from an open chain diolefin.
 9. Method of claim 4 wherein said one ligand is derived from an open chain oligo-olefin.
 10. Method of claim 4 wherein said one ligand is derived from a cyclic diolefin.
 11. Method of claim 4 wherein said one ligand is derived from a cyclic oligo-olefin.
 12. Method of claim 4 wherein said one ligand is derived from an acetylene.
 13. Method of claim 4 wherein said solvent is a nonhydroxylic solvent and wherein substantially all of the deposited metal is deposited on the substrate.
 14. Method of claim 4 wherein said reducing agent is hydrogen.
 15. Method of claim 1 wherein said metal is palladium.
 16. Method of claim 1 wherein said substrate comprises a particulate material having a particle size in the colloid size range.
 17. Method of claim 1 wherein said metal is platinum.
 18. Method of claim 1 wherein said metal is aluminum.
 19. Method for electrolessly depositing two or more metals selected from the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, aluminum, gallium, indium, and thallium on a substrate having a catalytic surface capable of influencing deposition of said metal which comprises mixing said substrate with (1) a solution comprising a pi-complex of each of said two or more metals dissolved in a nonaqueous solvent therefor, said mixing being at a temperature which does not exceed the thermal decomposition point of said complexes, and with (2) a reducing agent selected from the group consisting of hydrogen, formic acid, alkali metal hydrides, alkali metal borohydrides, dibenzyl, hydrazobenzene, hydroquinone, cyclohexene, tetralin, 2-cyclohexene-1-one, 4-vinylcyclohexene, cyclohexadiene, limonene, terpenes, and 1,4-dihydro-N-benzylnicotinamide, each of said complexes having at least one ligand in the form of an organic group containing at least one carbon-to-carbon multiple bond, said group by virtue of said multiple bond being capable of pi-electron bonding to the metal of said complex, thereby decomposing said complexes to form elemental metal, and depositing said elemental metals as a mixture on said substrate.
 20. Method of claim 19 wherein said metals are gold and palladium. 